A technology that is disclosed in PTL 1 has been proposed as a wireless communication system that transmits and receives a rotational wave (circularly polarized wave). In PTL 1, a transmitter has a function of setting a frequency between a given carrier frequency and zero, as a non-linear period path, for the given carrier frequency and transmitting a circularly polarized wave. Then, at a rotational frequency between a frequency of this carrier wave and zero, an electromagnetic wave that has an electric field vector which rotates with respect to a propagation axis is generated and transmitted. Then, it is disclosed that, for example, in a case where three transmission antennas are present, the three transmission antennas transmit electromagnetic waves of which phases are shifted (delayed) by 120 degrees. On the other hand, a receiver demodulates the electromagnetic waves that are received at the same frequency as that in the non-linear period path of the transmitter. Each of the transmitter and the receiver has a phase locked loop (PLL), and demodulates the electromagnetic wave that is received at the same frequency as that at the transmitter side, using the PLL.